Barley (Hordeum vulgare) L. is an important cereal crop in the diet and nutrition of humans and animals. In the US., the second largest producer of barley, 40% of the crop is utilized for human food products and 60% for animal feed. Ustilago hordei (Pers.) Lagerh is the casual agent for the disease covered smut of barley and is an opportunist agent in a range of human problems. The increased use of cytotoxic and immunosuppressive drugs and the escalation of AIDS in the population have exacerbated the role of opportunist fungi in human health problems. However limited research has been done on the genetics, and therapeutic control of these fungi. The objective of this project is to utilize a combination of modern molecular genetic manipulations and classical techniques to develop a clear understanding of the genetic variability and pathogenicity of U. hordei and translate this into a working model for the control of pathogenic fungal diseases under clinical and field situations. This will be accomplished by 1) the induction of auxotrophic and fungicide resistant genetic markers for classical and molecular genetic analyses with emphasis on gene and RFLP (restriction fragment length polymorphism) mapping 2) the physical characterization of the genome through the development and analysis of molecular karyotypes 3) investigation of protein polymorphism through PAGE (polyacrylamide gel electrophoresis) 4) ultra-structural elucidation of the roles of wild type and morphological mutant sporidial budding, conjugation and fimbriation in the pathogenicity of the susceptible host. These experimental approaches will simultaneously train students in understanding the development and employment of a range of microbial and molecular genetics principles and methodologies that have across the board application for both prokaryotic and eukaryotic research. The results obtained from these studies will increase the availability of barley for the diet and nutrition of humans and animals and also form an invaluable base for applied research in the biomedical field through a greater understanding of the genetics of microorganisms and their therapeutic control.